1. Field of the Invention
The present invention relates to a waterproof/drainage structure for a casing which is suitably used for electronic devices and the like having a pushbutton such as a notebook PC, a portable telephone, a transceiver, an electric reel, kitchenware, and a doorbell, and to an electronic device using the same.
2. Description of the Related Technology
In recent years, various functions are required of electronic devices relating to Information Technology (IT), such as a portable telephone and a personal computer. Of those, one of the functions frequency demanded by users is the waterproof function for the area around a pushbutton.
Conventionally, there have been proposed various techniques waterproofing the area around a pushbutton of an electronic device. For example, there has been proposed a key pad for waterproof appliance which retains: a sheet portion affixed onto the back surface of a casing of an electronic device; and a plurality of pushbuttons provided in the sheet portion, the key pad including an outer frame portion surrounding all of the pushbuttons, and a draining groove provided in the outer frame portion (refer to Patent Document 1 for example).
Further, there has been proposed a technique in which a casing of a portable telephone is provided with a discharge hole discharging water that has entered the interior (refer to Patent Document 2 for example).
Further, there has been proposed a waterproofing technique for a portable telephone having key buttons, a sheet, and contacts, the technique involving: dividing the portable telephone into an exterior appearance portion composed of the key buttons and the sheet and a function portion composed of the sheet and the contacts; and hermetically sealing the exterior appearance portion and the function portion separately from the outer and inner sides of the casing (see, for example, Patent Document 3).                [Patent Document 1] JP 08-180760 A        [Patent Document 2] JP 2000-307697 A        [Patent Document 3] JP 2001-148726 A        